Core drilling



P. BIGGS CORE DRILLING Feb. 6, 1951 Filed May 22, 1945 Pa u! Bjggs INVENTOR.

PATENT AGENT Patented F ch. 6, 1951 CORE DRILLING Paul Biggs, Imperial, Tex., assignor to Stanolind Oil and Gas Company, Tulsa,

tion of Delaware kla., a corpora- Application May 22, 1945, Serial No. 595,151

9 Claims. (c1. 255-14) This invention pertains generally to the art of sampling formationsby coring. More particularly, it deals with an improvement in the art'of sampling formations at the bottom of a hole by circulating cores from such formations to the surface in the drilling fluid.

In the art of sampling deep subterranean formations by circulating cores to the surface in the drilling fluid two general-methods have been practiced. In the first a core barrelhas been pumped to the bottom by direct circulation and held in position contiguous to the drill bit by the pressure of the drilling fluid. That is, the constricted ports aroundthe core barrel cause a pressure drop in the drilling fluid sufiicient to hold the barrel in position at the bit to receive the cores as they are cut. When the. barrel is full of cuttings or cores, the circulation of the fluid is reversed; i. e., the fluid is circulated downward in the well and upward in the drill stem, and the barrel containing the cuttings or cores is circulated to the surface in the drilling fluid. This method of coring has many advantages over previous methods of coring in which all-of the drill pipe had to be' retracted-in order to. recover acore. However, many of the limitations of the earlier methods areretained in this method in that the washing action of the drilling fluid tends to dissipate the core anda recovery as low' as to 30per cent is not uncommon, especially wherethe formation cored is relatively. porous. The use of thismethod also islimitedin that in order to remove the core from the drill pipe drilling must be halted, the drill pipe must be raised, the kelly removed, and means provided at the surface for catching the barrel and for circulating the drilling fluid back to; the settling pit as it rises out of thedrill stem during the time that the core is being pumped to the surface. This method is also of limited application in that the core must be recovered a core barrel, which must of necessity be located contiguous to the bit. .The above-described method has been improved by completely eliminating the use of a core barrel and circulating the core fragments to the surface through the drill string as they are out by reverse circulation of the drilling fluid. Under this improved method the recovery is substantially improved. For example, it is not uncommon to obtain a core recovery of 97 to 100 per cent in porous formations which under prevfiousmethods gavearecoveryof less than 50 percent. .This improved process has, however, not'receiv'ed wideapplication in the'art in'that 2 standard drilling apparatus commonly employed in rotary drilling cannot be adapted to this method without major changes. For example, in a standard drilling rig it is not uncommon to use 4%". drill pipe with a kelly which has an internal diameter of only 2-3". In order that cores may be circulated to the surface under this type of operation the drill pipe, kelly, swivel, etc., must have essentially identical inside diameters. That.

is, in order that the core will be lifted by the drilling fluid a core must be out which will practically fill the drill pipe, kelly, etc., and obviously no internal diameter in the path can be less than the diameter of the core. A core having a diameter appreciably smaller than the internal diameter of the drill pipe will tend to be bypassed by the drilling fluid and cores will be lodged in the drill pipe, shutting off the circulation of the drilling fluid. This obviously necessitates either using a second string of drill pipe having an internal diameter substantially equivalent to the internal diameter of the kelly or increasing the size of the kelly so that its internal diameter is substantially equal to the internal diameter of the standard drill pipe; Changes-of this nature require major expenditures and a great de: crease in drilling efliciency' "I have overcome the disadvantagesinherent in the above-mentioned coring processes and by my improvement standard drilling rigs used in ordinary drilling can be readily and quickly adapted to a reverse-circulation coring rig. My invention, therefore, comprises the location of a suitable core catcher in a drill strin at or near the lowerend of the kelly. Thus cores having-a diameter substantially equivalent to the internal diameter of the standard drill pipe may be cut, floated substantiallyto the surface in the drilling fluid, and caught in a core barrel so that the core can bereadily removed without removin all ofthe drill string from the well. n It is therefore an object of this invention to provide a novel apparatus to facilitate the recovery of samples of a formation from the bot-- tom of a drilling well. It is another object of this invention to provide a means for adapting a standard drilling rig so that it may be used for sampling formations by reverse-circulation; coring. A still further object of this invention is to provide a core catcher which may-be located in a drill string near the surface and which will. catch cores as they are being pumped to the surface in the drilling fluid without materially affecting the flow of drilling fluid through the. drill pipe. Other objects and advantages of this invention will become apparent as a description thereof proceeds.

My invention will be described with reference to the drawings, in which similar reference numerals are applied to the same or corresponding parts, and in which Figure 1 is a diagrammatic cross section of a drill string having incorporated one embodiment of my invention; and

Figure 2 is an alternate embodiment of my invention adapted to be placed in the drill string shown in Figure 1.

In Figure l drill pipe H] has attached at its lower end a core bit I l which will cut a core having a diameter slightly smaller than the internal diameter of the drill pipe ID. My core barrel I2 is located near the upper end of the drill pipe ill and attached thereto as shown. Preferably this core barrel is located contiguous to the kelly l3, inasmuch as all of the drill string above the core barrel l2 must be removedfrom the well each time a core is removed from the core barrel as will be shown in greater detail hereinafter. Obviously this barrel can be placed at any position in the drill string, provided that it must always be placed below a constriction in the internal diameter of the string; but to facilitate the removal of cores it is, as indicated above, preferably placed immediately below the kelly. The core barrel l2 may be attached, for example, to the kelly l3 through an adapter 14. The core barrel [2 has an internal diameter i5 substantially greater than the drill pipe internal diameter 16. Tubular perforate means I! is located at the upper end of core barrel I2. It comprises, for example, a tube having a multiplicity of perforations [8 in the walls and a partially closed lower and IS. The upper end 20 may be threaded for attachment to adapter 14. This tubular perforated means prevents a core from entering the constricted area above but does not impede the flow of drilling fluid.

Near the lower end of core barrel 12 a core catcher 2| is provided for retaining a, sample or 'core in the core barrel. More particularly, core catcher 2! is adapted to permit cores having a diameter substantially equal to drill pipe internal diameter IE to pass upward therethrough but to prevent core movement in the opposite direction.

Thus when circulation of the drilling fluid upward through the drill pipe and core barrel ceases, the core but for core catcher 2| would fall through drill pipe to the bottom of the well.

As indicated above, the internal diameter l5 of core barrel l2 being substantially larger than the drill pipe internal diameter it will permit free passage of drilling fluid around the cores which are retained in core barrel l2 by perforate means I'I. Thus large-diameter cores which would not pass through the Kelly [3 due to its smaller internal diameter 22 are retained in the drill string below the kelly and can be removed by merely raising the upper end of the drill pipe Hi to the surface and disconnecting the core barrel at its lower end 23.

In Figure 2 an alternative embodiment of my core barrel is shown. In this embodiment the sample or core is retained in an inner perforate core tube 25 which is adapted to retain the core at the center of the outer core barrel and thus permit free passage of the drilling fluid in the annulus 26. This inner perforate core tube 25 may be threadably attached to adapter 14 so that it may be removed from the core barrel I2 with adapter l4 and kelly I3 by disconnecting core barrel l2 at the upper end from adapter I4. A core stop 21 is located at some intermediate point in inner perforate core tube 25 and is adapted to limit the upward movement of cores therein and thus prevent a core from lodging in adapter [4 and shutting off circulation of the drilling fluid. Perforations l8 are provided both above and below this core stop 21. Near the lower end of inner perforate core tube 25 a core catcher 2| is fitted and serves the same purpose as the core catcher described in connection with Figure 1 hereof;

In operation core fragments cut from the bottom of the well while using reverse circulation of the drilling .fluid are pumped up the drill pipe H] with the fluid, and separated from the fluid in inner perforate core tube 25 for an appreciable period of time, preferably until the barrel is full of core and circulation is impeded by the lodging of cores in the constricted area of the drill pipe to below core barrel l2. The drill string is then lifted so that the kelly l3, adapter I4, and inner perforate core tube 25 may be disconnected from the remainder of the drill string for removal of the accumulated core from inner perforate core tube 25. By removal of core catcher 2! from the lower end of the inner perforate core tube the core can be removed for observation and filing.

While I have described my invention with reference to particular embodiments in which cores are floated to the surface in the drilling fluid as they are cut from the bottom of the well by bit ll, it will be apparent that my invention is not limited to the particular embodiments shown. For example, my core catcher is adapted to catch core barrels such as are employed in the firstdescribed method used in the prior art. This invention is therefore to be limited only by the scope of the appended claims.

I claim: a

1. In a rotary core drill apparatus in which cores are out from the formations near the bottom of a well and pumped to the surface in the drilling fl'uid through the drill string the improvement comprising means in the upper end of said drill string to catch said cores and a fluid passage through said firstmamed means whereby the catching of a core will not materially affect the flow of said drilling fluid.

2. In a rotary core drill'apparatus in which cores are out from the formations near the bottom of a well and pumped to the surface in the drilling fluid through the drill pipe the improvement comprising a core barrel connected to said drill pipe adjacent to the upper end thereof, said core barrel having an internal diameter "substantially greater than the internal diameter of said drill pipe, perforate means within said core barrel, said perforate means being adapted to separate said cores from said drilling fluid, and means to retain said cores in said core barrel.

3. In a rotary core drill apparatus in which cores are cut from the formations near the bot-- tom of a well and pumped to the surface in the drilling fluid through the drill pipe the improvement comprising a core barrel connected to said drill pipe adjacent to the upper end thereof, said core barrel having an internal diameter substantially greater than the internal diameter of said drill pipe, perforate means at one end of said core barrel, and core retainer means at the other end whereby said cores will'be caught in said core barrel without materially impeding the flow of drilling fluid therethrough.

4. In a rotary core drill apparatus in which cores are cut from the formations near the bottom of a well and pumped to the surface in the drilling fluid through the drill pipe the improvement comprising an enlargement in the flow channel within said drill pipe, a perforated core tube within said enlargement, means at the upper end of said core tube to prevent the passage of cores therethrough, and means at the lower end of said core tube adapted to permit said cores to enter said core tube and to prevent exit of said core, the overall diameter of said core tube being substantially smaller than the internal diameter of said enlargement, whereby said core is retained in said core tube without materially affecting the flow of drilling fluid through said drill pipe.

5. In a rotary well drilling apparatus employing a drill string, a core bit at the lower end of said drill string, said core bit being adapted to cut a core having a diameter substantially equal to the drill pipe internal diameter from the formations at the bottom of said well, a kelly having an internal diameter substantially less than said drill pipe internal diameter, a core catcher in said drill string at a substantial distance above said core bit but below any substantial restriction in the internal diameter of said drill string and a fluid passage through said core catcher whereby said cores may be pumped up said drill string with the drilling fluid, retained in said core catcher and removed from said core catcher while drilling proceeds, for observation without removing all of said drill string from said well.

6. In a rotary well drilling apparatus employing a drill string, a core bit at the lower end of said drill string, a kelly having an internal diameter substantially less-than the internal diameter of said drill pipe, the improvement which comprises a core barrel adjacent said kelly and communicating at its lower end with said drill string, said core barrel comprising a resilient constriction in a lower portion thereof adapted to permit only the upward passage of the suspended core and drilling fluid, and means in the upper portion of said core barrel adapted to prevent the travel of the core while permitting the substantially unimpeded flow of the drilling fluid from said core barrel.

7. In a method of sampling formations wherein a plurality of cores are cut by a drill bit in the process of drilling the formations and the core samples are retrieved for inspection at the surface, the improvement comprising the steps of floating the individual cores upwardly within the drill pipe, entrapping a plurality of successive core samples within the uppermost portion of the drill string while permitting the drilling fluid to pass substantially unrestricted from the drill pipe, periodically terminating the drilling operation and circulation of drill fluid, and retriev ingthje accumulated core samples.

8 In a rotary core drill apparatus in which coresare cut from the formations near the bottom of a ell and pumped to the surface in the drilling through the drill string the improvement comprising a core barrel within and adjacent to the upper end of said drill string, a core tube within said core barrel, the overall diameter of sa core tube being substantially smaller than t nterior diameter of said core barrel whereby uid passage is left therebetween, means at upper end of said core tube to prevent the age of cores therethrough, means at the lower 'd, of said core tube adapted to permit said within the drill pipe, the improvement comprising a core barrel adjacent the upper end of said drill pipe, the internal diameter of said core barjrel being substantially greater than the internal diameter of said drill pipe, a resilient core re- 'tainer within said core barrel adapted to permit the flow of drilling fluid and the core thereabove, and core stop means within said core barrel and above said resilient core retainer adapted to en- ;trap the core therebelow within said core barrel and to permit fluid flow thereabove, whereby said 1 core is retained within said core barrel adjacent the upper end of the drill pipe withoutmaterially retarding the flow of drilling fluid through said drill pipe.

PAUL BIGGS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 18,500 Stone June 14, 1932 797,622 Smith Aug. 22, 1905 994,866 Muhleisen 1 June 13, 1911 1,071,199 Andrews Aug. 26, 1913 1,280,159 Carmichael Oct. 1, 1918 1,484,995 Pace Feb. 26, 1924 1,623,543 Jones et al Apr. 5, 1927 2,021,184 Hill Nov. 19, 1935 2,145,192 Pennington Jan. 24, 1939 2,216,962 Sewell Oct. 8, 1940 2,217,203 Hill Oct. 8, 1940 2,329,405 Mann Sept. '14, 1943 FOREIGN PATENTS Number Country Date 26,451 Great Britain 1911 es to enter said core tube and to prevent exit Certificate of Correction Patent No. 2,540,385 February 6, 1951 PAUL BIGGS It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 5, line 35, strike out the Words and comma While drilling proceeds, and insert the same after catcher, first occurrence, line 34, same column;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 10th day of April, A.

THOMAS r. MURPHY,

Assistant Gammz'ssz'oner of Patents. 

